Q. A toothpaste company want to know if its new product increases the length of time in-between dentist visit to its user. The company sets a target for 180 days to determine if its product prevents dentists' visits longer than other toothpaste. A random sample of 49 customers is taken with a mean of 186 days and standard deviation of 20. Set up a one tail test with an alpha equal to 0.05.
(2) Consider the computer output below:
|
Variable
|
N
|
Mean
|
Standard Deviation
|
O
|
|
x
|
15
|
8.69
|
?
|
0.443
|
(i) Calculate the missing value indicated by the question mark
(ii) Calculate a 95% confidence interval about the mean. What conclusion will you draw from this result
(iii) The example above is taken from an experiment done by a freight company that wanted to test the claim that deliveries were completed within 8 working days being sent. What conclusion can be drawn about delivery times?